1. Field of Technique
The present invention relates to a liquid ejection apparatus such as an inkjet type printer and a method for switching types of liquid supplied to a liquid ejection head of the liquid ejection apparatus.
2. Background Art
Typically, an inkjet type printer (hereinafter, referred to as a printer) is broadly known as a liquid ejection apparatus that ejects liquid onto a target. In the printer, ink is supplied from an ink cartridge, which retains ink, to a recording head (a liquid ejection head) that ejects the ink (the liquid). The recording head performs printing by ejecting the ink from a nozzle defined in a nozzle forming surface of the recording head onto a sheet of recording paper, or a target. In some of the printers, the ink cartridge is located at a position spaced from the recording head. In this case, the ink is supplied from the ink cartridge to the recording head through a tube routed in the printer.
To switch the ink ejected from the nozzle of the recording head to a different type of ink, supply of the ink from the currently used ink cartridge to the recording head is stopped. In this state, the ink is drained from the tube through the nozzle of the recording head. Subsequently, the different type of ink is supplied to the recording head from an ink cartridge that retains the ink through the tube.
However, such drainage of the ink from the tube, which is carried out when the ink to be ejected is switched from one type to another, increases wasteful consumption of the ink. To suppress such waste, Japanese Laid-Open Patent Publication No. 2006-175626 describes a printer in which a switching device connected to tubes extending from respective ink cartridges is arranged in the vicinity of the recording head.
In this printer, the type of the ink to be supplied to the recording head is switchable between a first type of ink (first liquid) and a second type of ink (second liquid) through the switching device. Specifically, in the switching device, a downstream end of a first passage (a first supply passage) that supplies the first type of ink and a downstream end of a second passage (a second supply passage) that supplies the second type of ink are joined into each other. A head supply passage that supplies the ink to the recording head is defined between the joining point and the recording head. Further, the switching device receives a first diaphragm (a first ON-OFF valve), a second diaphragm (a second ON-OFF valve), and a spring. The first diaphragm selectively opens and closes the first passage and the second diaphragm selectively opens and closes the second passage. The spring urges the first and second diaphragms to open. By closing one of the first and second diaphragms against the urging force of the spring and opening the other, the state of supply is switched between the first type of ink and the second type of ink.
To supply the first type of ink to the recording head, the switching device opens the first diaphragm of the first passage and closes the second diaphragm of the second passage. Contrastingly, to supply the second type of ink to the recording head, the second diaphragm of the second passage is opened and the first diaphragm of the first passage is closed.
The printer includes two sliders provided in the switching device. The sliders linearly move to swing corresponding pressing members, or a first pressing member (a first actuator) and a second pressing member (a second actuator). This selectively opens and closes the corresponding first and second diaphragms. This makes it necessary to create space for allowing movement of the two sliders in the switching device. As a result, the switching device becomes large-sized, enlarging the printer.
There is also a switching device without springs that urge first and second ON-OFF valves to open. In this case, if one of the first and second ON-OFF valves is maintained open with the other held in a closed state for a long time, the closed one of the ON-OFF valves may adhere to the valve seat and thus be prevented from opening even though the first ON-OFF valve and the second ON-OFF valve are both operated to open.